Genetics: From Genes to Genomes
Genetics: From Genes to Genomes
6th Edition
ISBN: 9781259700903
Author: Leland Hartwell Dr., Michael L. Goldberg Professor Dr., Janice Fischer, Leroy Hood Dr.
Publisher: McGraw-Hill Education
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Chapter 7, Problem 21P

The physicist Stephen Hawking, famous for his theories about black holes, has lived past the age of 70 with amyotrophic lateral sclerosis (ALS), a paralyzing neurodegenerative disease that is usually fatal at a much younger age. Recently, geneticists discovered that a major cause of ALS is the unusual expansion of a hexanucleotide repeat (5′-GGGGCC-3′) that lies within a gene called C9ORF72, at a location outside of the gene’s open reading frame (ORF). A single expanded allele is sufficient to cause ALS, but the reason the disease allele is dominant remains unclear. Some experimental results support the theory that the allele makes a toxic RNA containing the expanded repeat. If this theory is correct, in what ways is the mutant ALS-causing allele similar to the mutant allele that causes Huntington disease? In what ways is it similar to the mutant allele that causes fragile X syndrome?

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You learned in Problem 21 in Chapter 7 that theneurodegenerative disease ALS can be caused by expansion of a hexanucleotide repeat region (5′-GGGGCC-3′)outside of the open reading frame (but within the firstintron) of the gene called C9ORF72. While a normalC9ORF72 allele has 2–23 copies of the hexanucleotiderepeat unit, dominant disease-causing alleles have hundreds or even thousands of copies. Researchers observed that the first intron of theC9ORF72 disease allele is transcribed not only fromthe normal template strand of DNA, but also from thenontemplate strand. Even more unusual, both types ofrepeat-region transcripts are translated in all six readingframes in an AUG-independent manner—a processcalled repeat-associated non-ATG translation, or RANtranslation. These discoveries led to the hypothesisthat the proteins made from the repeats mightcontribute to ALS.a. What polypeptides are made from the repeat-regiontranscripts?b. According to the RAN translation hypothesis, whyare…
Knowing that the genetic code is almost universal, a scientist uses molecular biological methods to insert the human β-globin gene (Shown in Figure 17.11) into bacterial cells, hoping the cells will express it and synthesize functional β-globin protein. Instead, the protein produced is nonfunctional and is found to contain many fewer amino acids than does β-globin made by a eukaryotic cell. Explain why.
A normal hemoglobin protein has a glutamic acid at position 6; in sickle-cell hemoglobin, this glutamic acid has been replaced by a valine. List all the possible mRNA codons that could be present for each type of hemoglobin. Can a single base change result in a change from Glu to Val in hemoglobin?

Chapter 7 Solutions

Genetics: From Genes to Genomes

Ch. 7 - Like the yellow Labrador retrievers featured in...Ch. 7 - Remember that Balancer chromosomes prevent the...Ch. 7 - Figure 7.14 shows examples of base substitutions...Ch. 7 - Figure 7.14a shows the mutagen 5-bromouracil 5-BU,...Ch. 7 - So-called two-way mutagens can induce both a...Ch. 7 - In 1967, J. B. Jenkins treated wild-type male...Ch. 7 - When a particular mutagen identified by the Ames...Ch. 7 - Prob. 18PCh. 7 - The Ames test uses the reversion rate His- to His...Ch. 7 - The mutant FMR-1 allele that causes fragile X...Ch. 7 - The physicist Stephen Hawking, famous for his...Ch. 7 - Aflatoxin B1 is a highly mutagenic and...Ch. 7 - In human DNA, 70 of cytosine residues that are...Ch. 7 - Bromodeoxyuridine BrdU is a synthetic nucleoside...Ch. 7 - Albinism in animals is caused by recessive...Ch. 7 - a. In Figure 7.22b, what can you say about the...Ch. 7 - Imagine that you caught a female albino mouse in...Ch. 7 - Plant breeders studying genes influencing leaf...Ch. 7 - In humans, albinism is normally inherited in an...Ch. 7 - a. Seymour Benzers fine structure analysis of the...Ch. 7 - a. You have a test tube containing 5 ml of a...Ch. 7 - Prob. 32PCh. 7 - The rosy ry gene of Drosophila encodes an enzyme...Ch. 7 - Nine rII- mutants of bacteriophage T4 were used in...Ch. 7 - In a haploid yeast strain, eight recessive...Ch. 7 - In Problem 24, you learned that Bloom syndrome is...Ch. 7 - The pathway for arginine biosynthesis in...Ch. 7 - In corn snakes, the wild-type color is brown. One...Ch. 7 - In a certain species of flowering plants with a...Ch. 7 - The intermediates A, B, C, D, E, and F all occur...Ch. 7 - In each of the following cross schemes, two...Ch. 7 - Prob. 42PCh. 7 - The following complementing E. coli mutants were...Ch. 7 - In 1952, an article in the British Medical Journal...Ch. 7 - Mutations in an autosomal gene in humans cause a...Ch. 7 - Antibodies were made that recognize six proteins...Ch. 7 - Prob. 47PCh. 7 - Prob. 48PCh. 7 - In addition to the predominant adult hemoglobin,...Ch. 7 - Most mammals, including New World primates such as...Ch. 7 - Humans are normally trichromats; we have three...
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